Magnetic memory device

ABSTRACT

A magnetic memory device includes a plurality of magnetoresistive elements arranged on a first plane in a matrix form, a plurality of first writing lines which are arranged on a second plane different from the first plane adjacent to the magnetoresistive elements, a first address decoder which selects a desired one from the plurality of first writing lines, a plurality of second writing lines crossing the plurality of first writing lines on a third plane different from the second plane and having parts adjacent to the plurality of magnetoresistive elements on the second plane and parallel to the plurality of first writing lines, and a second address decoder which selects a desired one from the plurality of second writing lines.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priorityfrom the prior Japanese Patent Applications No. 2001-090768, filed Mar.27, 2001; No. 2001-095976, filed Mar. 29, 2001, the entire contents ofboth of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a magnetic memory device using aferromagnetic material, and more particularly to a non-volatilesolid-state memory utilizing a ferromagnetic tunneling junction (MTJ).

[0004] 2. Description of the Related Art

[0005] In recent years, in a sandwich film in which one layer of adielectric body is inserted between two magnetic metallic layers, therehas been discovered a magnetoresistive element which can read a changein resistance by passing a tunneling current to a film surface in thevertical direction and utilizing this tunneling current, which is aso-called MTJ element (Magnetic Tunnel Junction element).

[0006] In regard to the ferromagnetic tunneling junction, there has beenreported the fact that a rate of change in magnetoresistance which isnot less than 20% can be obtained (see J. Appl. Phys. 79,4724 (1996),for example). Therefore, the possibility of application to a magnetichead or a magnetic random access memory (MRAM) has been increased (seeU.S. Pat. No. 5,640,343, and U.S. Pat. No. 5,734,605). Thisferromagnetic tunneling junction forms a tunneling barrier layercomprising AlO_(x) by forming a film of a thin Al layer having athickness of 0.4 nm to 2.0 nm on a ferromagnetic electrode and thenexposing its surface to pure oxygen or oxygen glow discharge or oxygenradical.

[0007] Further, there is proposed a ferromagnetic single tunnelingjunction having a structure in which an antiferromagnetic layer is givento one ferromagnetic layer of the ferromagnetic single tunnelingjunction and that ferromagnetic layer is determined as a magneticallypinned layer (see Jpn. Pat. Appln. KOKAI Publication No. 10-4227). Thisferromagnetic tunneling junction element (ferromagnetic single tunnelingjunction), however, likewise has a problem that the rate of change inthe magnetoresistance (MR ratio) is greatly reduced when the value ofthe voltage to be applied to the ferromagnetic tunneling junctionelement is increased in order to obtain a desired output voltage value.

[0008] Furthermore, there is proposed a ferromagnetic tunneling junctionhaving magnetic particles dispersed in a dielectric body or aferromagnetic double tunneling junction (see Jpn. Pat. Appln. KOKAIPublication No. 9-260743, Phys. Rev. B 56(10), R5747 (1997), Journal ofthe Magnetic Society of Japan 23, 4-2, (1999), Appl. Phys. Lett. 73(19),2829 (1998)). In these junctions, since the rate of change in themagnetoresistance which is not less than 20% can be obtained, thepossibility of application to a magnetic head or a magnetoresistivememory device has emerged.

[0009] In these ferromagnetic double tunneling junctions, sincereduction in the MR ration involved by a bias voltage is small ascompared with the ferromagnetic single tunneling junction, they have acharacteristic that a large output can be obtained.

[0010] A magnetic memory element using the ferromagnetic single ordouble tunneling junction is non-volatile, and a writing/reading time isas fast as 10 nsec or below. It has a potential ability that a number oftimes of rewriting is not less than 10¹⁵ and a cell size can be reducedas small as a DRAM (Dynamic Random Access Memory).

[0011] In particular, the magnetic memory element using theferromagnetic double tunneling junction can suppress reduction in therate of change in the magnetoresistance even if a value of a voltage tobe applied to the ferromagnetic tunneling junction element is increasedin order to obtain a desired output voltage value as described above,and hence a large output voltage can be assured, thereby demonstrating acharacteristic which is preferable as the magnetic memory element.

[0012] However, since the magnetic memory element using theferromagnetic single or double tunneling junction utilizes aferromagnetic material, it has a problem that power consumption at thetime of writing is large when a memory capacity is increased and a cellwidth of the ferromagnetic tunneling junction is decreased, as comparedwith a competing memory such as a FeRAM (Ferroelectric Random AccessMemory), a flash memory or the like.

[0013] When a switching magnetic field is increased, not only powerconsumption during writing is increased, but also the density of anelectric current caused to flow to a word line and a bit line in orderto invert a spin is increased and a problem of EM (Electro-Migration)occurs when the high density of an MRAM (Magnetic Random Access Memory)is realized and the design rule is minimized.

[0014] Based on a result of the electromagnetic field simulation for anelectromagnetic field distribution and the intensity in a directionwithin an MTJ cell plane when the design rule is 0.1 μm, it can beunderstood that the intensity of the electromagnetic field is the orderof 10 Oersted (Oe) at the highest even in cases where the density of theelectric current caused to flow to wirings is assumed to be 5×10⁶ A/cm².

[0015] Furthermore, when the capacity of the MRAM is approximately 1Gbit and a distance between adjacent cells is approximately 0.1 μm, themagnetic field applied to the adjacent cells becomes approximately 80%of the magnetic field applied to cells on the wirings, and there mayoccur a problem of the interference between cells, i.e., so-calledcrosstalk.

[0016] In order to solve the problem of crosstalk, there is proposedchanging a direction of a magnetization easy axis between the adjacentcells to a different direction (see U.S. Pat. No. 6,005,800). The shapeof cells must be formed without irregularities in order to use thismethod. However, when the capacity of the MRAM is increased and the cellsize is reduced, the forming accuracy is hard to be controlled, andthere are irregularities in the switching magnetic field of cells, whichresults in a problem that the crosstalk can be hardly eliminated.

[0017] Moreover, the size of the switching magnetic field depends on acell size of the MTJ, a cell shape, a magnetization characteristic of amaterial, a film thickness or the like. For example, when the cell sizeof the MTJ becomes small as described above, the switching magneticfield of the spin is increased due to the influence of the demagnetizingfield.

[0018] As to the cell shape, a magnetic domain is produced at an endportion in case of a rectangular cell shape, the remanence is decreased,and the steplike Barkhausen jump occurs. In addition, variations aregenerated in the switching magnetic field depending on how the magneticdomain is produced. When the cell shape is elliptical, a single domainstructure can be obtained and the MR ratio is not lowered. However,there is a problem of a large degree of the increase in the switchingmagnetic field as a function of the reduction in the cell width.

[0019] Additionally, in order to solve these problems, there areproposed a structure characterized in that a magnetic memory cell isprovided at a part where bit and word lines cross each othersubstantially at right angles and shape of the cell is asymmetric withrespect to the magnetization easy axis, and a structure in which theeasy axis is somewhat inclined from the direction of wirings (see U.S.Pat. No. 6,104,633).

[0020] As to the shape control, however, when the density of the MRAM isincreased and the cell size is reduced as described above, the formingaccuracy can not be disadvantageously controlled, and irregularities aregenerated in the switching magnetic field of the cell.

[0021] Further, in the structure having the easy axis of the cell beingsomewhat inclined from the direction of wirings, the switching magneticfield is reduced, but the problem of crosstalk becomes serious when thedensity is increased.

[0022] In order to solve these problems (increase in the switchingmagnetic field involved by crosstalk and reduction in the cell width),it can be considered that the magnetic shield must be provided to thewirings (see U.S. Pat. No. 5,659,499, U.S. Pat. No. 5,940,319, and WO200010172). When the magnetic shield is provided to the wirings, notonly a value of the electromagnetic field is increased but also theproblem of crosstalk can be solved.

[0023] Assuming that the cross-sectional aspect ratio of the bit lineand the word line is 1:2 and distances between the bit line and arecording layer and between the word line and the recording layer are 10nm and 50 nm, respectively and that the density of the electric currentcaused to flow to them is 2.5×10⁶ A/cm² which is a realistic value, thecurrent magnetic field generated in the MTJ cell is 87 Oersted (Oe).However, when the cell width is determined to be not more than 0.1 μm byusing CogoFe₁₀ which is softest in Co—Fe having the large MR ratio, theswitching magnetic field reaches approximately 200 Oersted (Oe), and afurther new cell structure and a memory structure are required in orderto realize a 1 Gbit MRAM.

[0024] Furthermore, in case of using the ferromagnetic tunnelingjunction as a magnetic head material for HDD (Hard Disk Driver), thereis proposed a structure in which a hard bias layer is provided adjacentto the ferromagnetic tunneling junction in order to reduce theBarkhausen noise (see U.S. Pat. No. 5,729,410, and U.S. Pat. No.5,966,012). However, using the hard bias layer is not preferable forreducing the switching magnetic field.

[0025] As described above, when the density of the MRAM is increased,the MRAM has a problem of large power consumption during writing, aproblem of crosstalk and a problem of electromigration (EM) as comparedwith competing memories such as a FeRAM, a flash memory and the like.

[0026] Therefore, there is desired realization of a magnetic memorydevice having a memory structure and a wiring structure which can reducepower consumption during writing and does not have a problem orcrosstalk or EM.

BRIEF SUMMARY OF THE INVENTION

[0027] According to a first aspect of the present invention, there isprovided a magnetic memory device comprising:

[0028] a plurality of magnetoresistive elements arranged on a firstplane in rows and columns;

[0029] a plurality of first writing lines arranged on a second planedifferent from the first plane adjacent to the magnetoresistiveelements, respectively;

[0030] a first address decoder which selects a desired one from aplurality of the first writing lines;

[0031] a plurality of second writing lines crossing the plurality offirst writing lines on a third plane different from the second plane andhaving parts adjacent to the plurality of magnetoresistive elements andparallel to the plurality of first writing lines; and

[0032] a second address decoder which selects a desired one from theplurality of second writing lines.

[0033] According to a second aspect of the present invention, there isprovided a magnetic memory device comprising:

[0034] a first writing line arranged on a first plane;

[0035] a second writing line arranged on a second plane different fromthe first plane and has a first part extended from one directionvertical to the first writing line, a second part connected to the firstpart at one end portion thereof and overlaps the first writing line, anda third part connected to the second part at the other end portionthereof, and extended vertically to the first writing line on anopposite side of the first part, the relationship of 2a>b>0 beingobtained provided that a line width of the first and second writinglines is a and a shortest distance between a central line of the firstpart and a central line of the third part of the second writing line isb; and

[0036] a magnetoresistive element sandwiched between the first writingline and the second part of the second writing line and connected toeither the first writing line or the second writing line.

[0037] According to a third aspect of the present invention, there isprovided a magnetic memory device comprising:

[0038] a plurality of ferromagnetic tunneling junction elements arrangedon a first plane in a matrix form, each having at least twoferromagnetic layers including a magnetic recording layer and at leastone tunneling barrier layer therebetween; and

[0039] a plurality of soft magnetic bias layers provided at both ends ofthe plurality of ferromagnetic tunneling junction elements in amagnetization easy axial direction and having magnetism softer than themagnetic recording layer.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0040]FIG. 1 is a schematic view showing a memory cell layout in a firstembodiment according to the present invention;

[0041]FIG. 2A is a cross-sectional view taken along the line 2A-2A inFIG. 1;

[0042]FIG. 2B is a cross-sectional view taken along the line 2B-2B inFIG. 1;

[0043]FIG. 3 is a block diagram typically showing a structure of amemory cell array in embodiments according to the present invention;

[0044]FIG. 4A is a view illustrating a cell selection principle duringthe writing operation in a conventional cross point method;

[0045]FIG. 4B is a view illustrating a cell selection principle duringthe writing operation in the first embodiment;

[0046]FIGS. 5A to 5C are views typically showing variations of a crossshape of first and second writing lines in the first embodiment;

[0047]FIG. 6 is a view typically showing a memory cell layout in asecond embodiment;

[0048]FIG. 7A is a cross-sectional view taken along the line 7A-7A inFIG. 6;

[0049]FIG. 7B is a cross-sectional view taken along the line 7B-7B inFIG. 6;

[0050]FIG. 8 is a schematic view showing a memory cell layout in a thirdembodiment;

[0051]FIG. 9 is a schematic view showing a memory cell layout in afourth embodiment;

[0052]FIG. 10 is a schematic view showing a memory cell layout in afifth embodiment;

[0053]FIG. 11 is a perspective view showing a basic conformation of amagnetic memory element according to sixth to ninth embodiments;

[0054]FIG. 12 is a typical perspective view showing the arrangement ofMTJ cells in a conventional cross point;

[0055]FIG. 13 is a view comparing a switching magnetic field curve (A)obtained when using the basic conformation according to the presentinvention with a conventional switching magnetic field curve (B);

[0056]FIG. 14 is a circuit diagram showing an architecture of a magneticmemory device according to the sixth embodiment;

[0057]FIG. 15 is a circuit diagram showing an architecture of a magneticmemory device according to the seventh embodiment;

[0058]FIG. 16 is a circuit diagram showing an architecture of a magneticmemory device according to the eighth embodiment;

[0059]FIG. 17 is a view comparing a switching magnetic field curve (C)of the magnetic memory device according to the eighth embodiment with aconventional switching magnetic field curve (D);

[0060]FIG. 18 is a circuit diagram showing an architecture of a magneticmemory device according to the ninth embodiment;

[0061]FIG. 19 is a schematic plan view showing the state of an upperwiring, an underpart wiring and an MTJ cell in the ninth embodiment;

[0062]FIG. 20 is a schematic cross-sectional view showing one memorycell in the ninth embodiment;

[0063]FIG. 21 is a schematic view showing a memory cell layout in atenth embodiment;

[0064]FIG. 22A is a cross-sectional view taken along the line 22A-22A inFIG. 21;

[0065]FIG. 22B is a cross-sectional view taken along the line 22B-22B inFIG. 21;

[0066]FIG. 23 is a schematic layout view showing a memory cell structurein the tenth embodiment;

[0067]FIGS. 24A and 24B are schematic layout views showing memory cellstructures in an 11th embodiment;

[0068]FIG. 25 is a view illustrating a cell selection principle duringthe writing operation in the 11th embodiment;

[0069]FIG. 26 is a schematic view showing a memory cell layout in a 12thembodiment;

[0070]FIG. 27A is a cross-sectional view taken along the line 27A-27A inFIG. 26;

[0071]FIG. 27B is a cross-sectional view taken along the line 27B-27B inFIG. 26;

[0072]FIG. 28 is a schematic plan view showing a basic conformation of amagnetic memory device including a soft magnetic bias layer;

[0073]FIGS. 29A to 29D are type drawings showing examples of the cellshape (plan views) of the magnetic memory device including the softmagnetic bias layer;

[0074]FIG. 30 is a view comparing a switching magnetic field curve (E)of a magnetic memory device according to a 13th embodiment with aswitching magnetic field curve (F) of the magnetic memory deviceaccording to the eighth embodiment;

[0075]FIG. 31 is an element cross-sectional view showing an example ofthe layer structure of an MTJ cell used in the embodiments according tothe present invention;

[0076]FIG. 32 is an element cross-sectional view showing another exampleof the layer structure of the MTJ cell used in the embodiments accordingto the present invention; and

[0077]FIG. 33 is an element cross-sectional view showing still anotherexample of the layer structure of the MTJ cell used in the embodimentsaccording to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0078] A memory cell of an MRAM usually has a structure in which aplurality of ferromagnetic materials are laminated. Information isrecorded by associating the fact that the relative arrangement ofmagnetization of a plurality of ferromagnetic materials constituting thememory cell is parallel or antiparallel with binary information “1” or“0”. Recorded information is written by switching a direction ofmagnetization of the ferromagnetic materials of each cell by anelectromagnetic field generated by causing an electric current to flowto writing lines arranged in the cross stripe form.

[0079] Power consumption when maintaining recorded information is zeroin principle, and the memory is a non-volatile memory by which recordedinformation is maintained even if a power supply is turned off. Recordedinformation is read by utilizing a phenomenon that the electricresistance of the memory cell varies depending on a relative angle ofthe direction of magnetization of the ferromagnetic materialsconstituting the cell and a sense current or depending on a relativeangle of magnetization between a plurality of ferromagnetic layers,i.e., a so-called magnetoresistive effect.

[0080] In order to develop the MRAM which has a degree of Gbit classintegration, there are some problems to be solved. One of such problemsis reduction in a writing current. In the conventionally proposed MRAM,the current is passed to wirings, and a resulting magnetic field is usedto invert magnetization of a recording layer of the MTJ element.

[0081] Although the intensity of the magnetic field generated from thewirings varies depending on a current value of the wirings and adistance between the wiring and the MTJ element, it is approximatelyseveral Oe/mA in conventionally known report examples. Further, amagnetization inversion threshold value (which will be defined as aswitching magnetic field Hsw hereinafter) of the recording layer of theMTJ element is increased in inverse proportion to a size of the MTJelement in the direction of the magnetization hard axis (which will bedefined as a cell width w hereinafter), which is expressed as follows:

Hsw=Hsw ₀ +A/w  (1)

[0082] where Hsw0 is a switching magnetic field of a bulk. Furthermore,A is a constant which depends on a shape, a material or the like of thecell, and a conventionally know value of A is 10 to 20 Oe μm.

[0083] Taking the reliability of the wiring into consideration,electromigration gives one restriction. The electromigration isaccelerated with the wiring current density, and the current densityupper limits in the Al—Cu wiring and the Cu wiring currently used inmanufacture of LSI are approximately 10⁶ A/cm² and 10⁷ A/cm²,respectively.

[0084] Considering manufacture by the rule of 0.1 μm required forrealizing a degree of Gbit class integration, the upper limit of a valueof the current which can flow to the wiring is approximately 1 mA evenif the Cu wiring is used, and a value of the resulting magnetic field isapproximately several Oe. On the other hand, the switching magneticfield of the MTJ whose size is approximately 0.1 μm is several tens ofOe or above in accordance with the expression (1). That is, the Gbitclass MRAM is hardly realized with the current technology.

[0085] On the other hand, there is a problem of interference duringwriting between adjacent cells as another problem for development of theMRAM. That is, in the MRAM, a plurality of writing lines are arranged soas to be substantially orthogonal to each other, and they form a crossmatrix. During the writing operation, two orthogonal writing lines areselected, and inversion of magnetization of the recording layer in theselected MTJ cell is thereby caused by a synthetic magnetic fieldgenerated at an intersection.

[0086] In this case, besides the selected cell, there is a half-selectedcell which receives the magnetic field from either the vertical wiringor the horizontal wiring. Therefore, in order to prevent erroneouswriting into the half-selected cell, a rewriting current value must beadjusted so as to invert the selected cell and not to invert thehalf-selected cell during the writing operation. In a large-scale array,since a distribution is generated in the switching magnetic field of theMTJ cells, an allowable range of the rewriting current value generallybecomes very small.

[0087] As described above, in order to develop the Gbit class MRAM, thetwo major problems are: (1) increase in the magnetic field generationefficiency from the wiring; and (2) increase in the allowable range ofthe rewriting current value in order to avoid erroneous writing into thehalf-selected cell during the writing operation. However, there is notknown a method which provides a structure suitable for the MTJ cellwhich is a vertical current element and solves the above two problems.The following embodiments provide a method which can solve such problemsand realize a high-speed low-power-consumption magnetic memory devicewhich has a recording capacity of not less than several Gbit.

[0088] Preferred embodiments according to the present invention will nowbe described hereinafter with reference to the accompanying drawings.

[0089] (First Embodiment)

[0090]FIG. 1 is a plan view typically showing a cell layout according toa first embodiment of the present invention. Moreover, FIG. 2A is across-sectional view of a memory cell taken along the line 2A-2A of FIG.1, and FIG. 2B is a cross-sectional view of the memory cell taken alongthe line 2B-2B of FIG. 1. It is to be noted that FIG. 1 is a bottom viewseen from a substrate surface side (lower side) for facilitatingunderstanding.

[0091] In FIG. 1, reference numerals 11 and 12 denote first writinglines; 21 and 22, second writing lines; 101 and 102, MTJ elements(cells); and 31 and 32, contact holes. In addition, in FIGS. 2A and 2B,reference numeral 41 designates a lower electrode; 501 and 502,diffusion areas of selected transistors; and 51, a word line of aselected transistor. The first writing lines and the second writinglines are electrically insulated. In addition, the second writing linesare electrically connected to the MTJ elements, and also serve as datalines.

[0092] As shown in FIG. 1, the memory cell in the magnetic memory deviceaccording to the first embodiment is mainly comprised of the firstwriting lines, the second writing lines and the MTJ cells. The firstwriting lines and the second writing lines are arranged on planesdifferent from each other and configured to sandwich the MTJ cells inthe direction vertical to the film surface. Incidentally, FIGS. 2A and2B show the structure in which the second writing lines are provided inthe upper layer of the first writing lines, but the reverse structure isalso possible.

[0093] The first writing lines and the second writing lines areorthogonal to each other when taking a bird's eye view of them, and formthe cross matrix. On the other hand, in the vicinity of an intersection,the first writing line and the second writing line run in parallel witheach other. The first writing line runs parallel for a fixed length andthen is bent at a right angle. As a result, the first writing line has azigzag shape. The second writing line is straight in a memory arrayarea.

[0094] The MTJ cell is arranged in an area where the first writing lineand the second writing line run in parallel with each other. Thedirection of a magnetization easy axis of the MTJ cell is arrangedvertically with respect to the second writing line running direction.

[0095] In the first embodiment, each of the first writing line and thesecond writing line is formed to have a width F (minimum line width inthe design rule), and an area of the memory cell is 10F².

[0096]FIG. 3 typically shows the structure of a memory cell array 100according to the embodiments of the present invention. In the memorycell array 100, the memory cells (MTJ cells) 101, 102 or the like arearranged in a matrix form.

[0097] As described above, the first writing lines 10 including 11, 12or the like and the second writing lines 20 including 21, 22 or the likeare substantially orthogonal to each other and connected to writing linedrivers through address decoders 110 and 120. The two address decoders110 and 120 are connected to an I/O line, respectively. As a result, awriting address with respect to an arbitrary memory cell can bedesignated by, for example, associating a higher part address and alower part address in signals from the address buss of the I/O line withselection of the first and second writing lines.

[0098] It is preferable that the MTJ cell has a spin valve structure inwhich a single tunneling barrier, a pinned layer having ferromagneticalloy or a multilayer film including Fe, Ni and Co and at least onelayer of an antiferromagnetic thin film such as PtMn being laminated isarranged on one side of the tunneling barrier and a recording layercomprised of ferromagnetic alloy including Fe, Ni and Co or a multilayerfilm is arranged on the other side.

[0099] Additionally, when the MTJ cell has the dual spin valvestructure, a further preferable conformation can be obtained becausedrop in the rate of change in the magnetoresistance relative to theelement application voltage can be reduced and the withstanding voltagecan be increased. The dual spin valve type structure means a structurein which the MTJ cell has two layers of the tunneling barriers, andpinned layers each having ferromagnetic alloy or a ferromagneticmulti-layer film including Fe, Ni and Co and a high-coercivity layerincluding at least one layer of an antiferromagnetic thin film of, e.g.,PtMn being laminated is arranged on the outer sides of the two tunnelingbarriers, whilst a recording layer comprised of ferromagnetic alloy or amulti-layer film including Fe, Ni and CO is arranged in an intermediatelayer sandwiched between the two tunneling barriers.

[0100] The method for writing information in the first embodiment willnow be described with reference to FIGS. 4A and 4B. FIG. 4A shows aconventionally utilized writing method and FIG. 4B illustrates a methodaccording to the first embodiment. The prior art example will be firstdescribed taking FIG. 4A as an example.

[0101] The process of magnetization of a ferromagnetic material having asub-micron size used for the MRAM can be explained by presuming a singledomain model with existence of the uniaxial anisotropy. At this moment,assuming that a threshold value of magnetization inversion (which willbe defined as a switching magnetic field Hsw hereinafter) is Hsw, Hsw,the magnetic field in the hard axis Hx and the magnetic field in theeasy axis Hy have the following relationship:

Hx ^(⅔) +Hy ^(⅔) =Hsw ^(⅔)  (2)

[0102]FIG. 4A shows a part of an asteroid curve typically showing theexpression (2).

[0103] In the prior art example, orthogonal magnetic fields in the twodirections are used, and a value of the unidirectional magnetic field(Hx, Hy) is determined so that the synthetic magnetic field thereofexceeds the threshold value. In the cross matrix type array structure,there exists a half-selected cell which receives the magnetic field inonly the hard axis direction or the easy axis direction. If an idealsingle domain model is presumed, an erroneous writing margin relative tothe half-selected cell is Hx=Hy, which is maximal. Therefore, thewriting operation is generally carried out maintaining the condition ofHx=Hy.

[0104] Assuming an ideal single domain structure, minimum values Hxminand Hymin of the unidirectional magnetic fields can be obtained bysolving the expression (2) and the following expression:

Hx=Hy  (3)

[0105] Also, the following expression can be obtained:

Hxmin=Hymin=2^(−{fraction (3/2)}) Hsw≈0.35Hsw

[0106] The value of the magnetic field is reduced as compared with thecase of simply synthesizing a half of the switching magnetic field,i.e., 0.5 Hsw.

[0107] The method of the first embodiment will now be described withreference to FIG. 4B.

[0108] This embodiment is characterized in that the first writing lineand the second writing line run in parallel with each other in thevicinity of the MTJ cell. However, an area in which the first writingline runs in parallel with the second writing line is limited, and thedirection of the magnetic field generated by the first writing lineactually has a finite angle relative to the magnetic field generated bythe second writing line.

[0109] This point will be again explained based on FIGS. 5A to 5C.

[0110] That is, as shown in FIG. 5A, the current slantingly flows in anarea where the first writing lines is bent. It is understood that thecurrent flows giving priority to an impedance minimum path. Although theflow actually becomes complicated since a current distribution isgenerated in the wiring, it can be understood that a relative angle ofthe magnetic fields Hx and Hy generated from the first writing wiringand the second writing wiring is determined by an angle θ=tan⁻¹(b/a)defined by a wiring width a and a length of a bent portion b in thefirst approximation.

[0111] In this case, selection of a cell by the magnetic fields obtainedfrom the first and second writing lines is carried out as follows. Asshown in FIG. 4B, the magnetic field Hy obtained from the second writingline is parallel with the magnetization easy axis. For example, when anarc having a radius Hxmin is described from an end y=Hymin of themagnetic field Hy, the arc crosses the switching curve represented bythe expression (2). That is, the synthetic magnetic field exceeds theswitching curve, and inversion of magnetization occurs. As describedabove, it is good enough to describe the arc having a radius Hx from theend of Hy and determine Hy and Hx in such a manner that the arc crossesthe switching curve. The relative angle of Hx and Hy is determined in arange of two intersections of the arc and the switching curves. Theerroneous writing margin relative to the half-selected cell becomesmaximum when Hx=Hy as similar to the prior art.

[0112] In FIGS. 4A and 4B, figures are drawn provided that Hxmin andHymin have the same length 2^(−{fraction (3/2)})Hxw. As apparent fromFIG. 4B, the arc crosses the switching curve and extends outwards in arange of approximately θ=20 to 90° in the first embodiment, and thisfigure shows that the writing magnetic field has a margin. The accuraterange is given as solutions of the expression (2) and the followingexpression (4):

Hx ²+(Hy−2^(−{fraction (3/2)}) Hsw)²=(2^(−{fraction (3/2)}) Hsw)²  (4)

[0113] That is, in the first embodiment, the current value required forwriting can be reduced as compared with the prior art, and this is asignificant advantage of the present invention.

[0114] Further, as can be understood from FIG. 4B, the writing currentvalue becomes minimum in the vicinity of a point at which the relativeangle of Hx and Hy is 30°-60°. The relative angle which provides theminimum value can be obtained when values of Hx and Hy are determined.Such a relative angle can be controlled by the wiring shape as describedabove.

[0115]FIG. 5B shows an example where the wiring width a and the bentlength b are equal to each other and the relative angle is set toapproximately 45°. Furthermore, FIG. 5C shows an example in which thebent portion is formed with an angle of inclination 45° in stead of theright angle. The great advantage of the present invention lines in thatthe optimum writing operation point can be set by controlling the shapeof the wiring bent portion in this manner.

[0116] When the line width of the two writing lines is a and the bentlength (distance between central lines of two parallel lines of the bentline) is b as described above, b=2a in FIG. 5A and b =a in FIGS. 5B and5C. Since the advantage of the present invention can be obtained if thecurrent path of one of the crossing two writing lines is vertical orsomewhat inclined, it is preferable to have the relationship 2a>b>0.

[0117] However, the operation with Hx and Hy being parallel with eachother is possible by the method for sufficiently making the length ofthe bent portion longer than the wiring width or the method of using amagnetic shield as will be described later.

[0118] (Second Embodiment)

[0119]FIG. 6 is a plan view typically showing from a substrate surfaceside a cell layout according to a second embodiment. FIG. 7A is across-sectional view of a memory cell taken along the line 7A-7A in FIG.6, and FIG. 7B is a cross-sectional view of the memory cell taken alongthe line 7B-7B. In FIGS. 6 and 7, reference numerals 11 and 12 denotefirst writing lines; 21 and 22, second writing lines; 101 and 102, MTJcells; 41 and 42, lower electrode wirings. The first writing line andthe second writing line are electrically insulated. Moreover, the secondwriting line is electrically connected to the MTJ cell and also servesas a data line.

[0120] In the second embodiment, a cell selection transistor is notprovided, and the MTJ cell is arranged at an intersection of a crossmatrix comprised of the second writing line which also serves as thedata line and the lower electrode wiring. Although the lower electrodewiring can be eliminated and the MTJ cell can be arranged by, e.g.,connecting the first and second writing wirings in the secondembodiment, care must be taken to a potential difference between thewirings caused during the writing operation. In such case, it ispossible to utilize a method of, e.g., avoiding application of a highvoltage by connecting an element which has rectification to the MTJ cellin series or providing rectification to the MTJ cell or the circuitcontrivance.

[0121] In the second embodiment, both the first writing line and thesecond writing line are formed to have a width F, and an area of thememory cell becomes 8F². The cell area is more reduced as compared withthe first embodiment because formation of a contact from the MTJ cell tothe lower semiconductor element is not necessary since the cellselection transistor is not used. It is to be noted that an area of thememory cell also varies depending on a shape of the bent portion. Whenthe length of the bent portion is shortened so as to approximate therelative angle of Hx and Hy to 30°-60°, the cell area is also reduced,which is preferable.

[0122] (Third Embodiment)

[0123]FIG. 8 is a plan view typically showing a cell layout according toa third embodiment, and rectangular MTJ cells 101 and 102 are used. Assimilar to the first embodiment, reference numerals 11 and 12 denotefirst writing lines, and 21 and 22 designate second writing lines.

[0124] Since the magnetization easy axis is stabilized along thelongitudinal direction of the rectangular ferromagnetic material due tothe shape anisotropy, the rectangular ferromagnetic material ispreferable to the memory cell application. As an aspect ratio, 1.5 orabove is preferable, and approximately 3 to 4 is suitable. It is goodenough to design the aspect ratio and the cell shape so as to obtain thedesired characteristic of the cell.

[0125] In the third embodiment, 3 is presumed as the aspect ratio of theMTJ cell. The second writing line has a width of 3F, and the firstwriting line has a width of 3F in a parallel area and a width of F in anorthogonal area. An area of the memory becomes 20F².

[0126] As in the third embodiment, when wiring formation is carried outby using different widths in the parallel area and the orthogonal area,the cell area can be greatly reduced, which is a preferableconformation.

[0127] (Fourth Embodiment)

[0128]FIG. 9 is a plan view typically showing a cell layout according toa fourth embodiment. The basic cell arrangement in this embodiment isthe same as that in the third embodiment. The fourth embodiment ischaracterized in that one ends of the second writing lines 21 and 22 areconnected to each other in the memory cell outer part and a commonwriting line 21 c is thereby formed. In such a structure, by passing thewriting electric current to the first writing line 11 and the commonwriting line 21 c, complementary writing can be realized with respect tothe MTJ cells 101 and 102.

[0129] Incidentally, although the common writing line is formed to thesecond writing line in the fourth embodiment, it may be formed by usingthe first writing line. That is, it is good enough that themagnetization directions of the recording layers of the adjacent cellsare constantly anti-parallel with each other. Incidentally, it isneedless to say that the structure satisfying this condition is includedin the present invention without departing from a scope of theinvention.

[0130] In the fourth embodiment, 3 is presumed as an aspect ratio of thetunneling junction element. The second writing line has a width of 3Fand the first writing line has a width of 3F in the parallel area and awidth of F in the orthogonal area. An area of a single memory cellbecomes 28F².

[0131] (Fifth Embodiment)

[0132]FIG. 10 is a plan view typically showing a cell layout accordingto a fifth embodiment. The fifth embodiment is characterized in that thefirst writing line and the second writing line have the same serriformshape and they rotate 90° to cross each other. In the fifth embodiment,there are two types of areas in which the first and second writing linesrun in parallel with each other. That is, in the drawing, one is an areadefined by a broken line surrounding the MTJ cell 101, and the firstwriting line and the second writing line run vertically to a lower sideof the page space. The other one is an area defined by a broken linesurrounding the MTJ cell 102, and the first writing line and the secondwriting line run in parallel to the lower side of the page space. In thefifth embodiment, the aspect ratio of the MTJ cell is 1, the first andsecond writing lines have a width of F, and an area of the memory cellbecomes 8F².

[0133] The magnetization easy axes of the MTJ cells 101 and 102 arrangedin different areas must be different from each other by 90°. AlthoughFIG. 10 shows an outside shape of the MTJ cell having the aspect ratioof 1, the fifth embodiment is not restricted thereto. Control over themagnetization easy axis can be readily realized by changing the cellshape as described above. In addition, besides the cell shape, themagnetic coupling relative to a third ferromagnetic film may beutilized, and crystal magnetic anisotropy of the ferromagnetic filmconstituting the cell may be used.

[0134] There are two modes for erroneous writing into the half-selectedcell. One is the mode in cases where inversion of magnetization occursdue to the unidirectional magnetic field at the time of half-selection,and this includes a creep phenomenon which can be a problem wheninversion of magnetization involving movement of a magnetic wall occurs.In this embodiment, the magnetic field applied to the half-selected cellcan be minimized during the writing operation as compared with the priorart, and the erroneous writing margin in this mode can be increased.

[0135] On the other hand, the other one is the mode in cases where thehalf-selected cell can be inverted due to a leakage field from thevicinity of the selected cell. This is, for example, the case that thehalf-selected cell which senses Hx is inverted due to leak of Hy appliedto the selected cell. This is erroneous writing which occurs in a cellclosest to the selected cell, and the probability of occurrence of suchwriting is higher than that in the erroneous writing mode.

[0136] In the fifth embodiment, for example, when the MTJ cell 101 isselected, the magnetization easy axis of the half-selected MTJ cell 102and that of the MTJ cell 101 provided to the first writing wiring 11 aredifferent from each other by 90°. Additionally, the MTJ cells 101 and102 are arranged with offsets in the directions of x and y. Therefore,the leakage field from the second writing wiring 21 is applied to thehalf-selected MTJ cell 102 with angles relative to the directions of themagnetization easy axis and the magnetization hard axis. Thus, theeffective leakage field value can be lowered, and the erroneous writingmargin can be further increased.

[0137] Although the first and second writing lines have the sameserriform shape in the fifth embodiment, a conformation different fromthis structure can be also realized. That is, the erroneous writingmargin can be increased if it is possible to realize both or either of(1) the fact that the magnetization easy axes of adjacent cells form therelative angle and (2) the fact that adjacent cells have offsets in thedirections of x and y. It is needless to say that the structuresatisfying this condition is included in the present invention withoutdeparting from the scope of the invention.

[0138] The first to fifth embodiments have illustrated the example inwhich the first writing line and the second writing line are arranged soas to be partially parallel to each other at an intersection of the twowriting lines, and the erroneous writing margin of the half-selectedcell is increased by utilizing the inclination of the electric currentpath of one zigzag writing line which is formed between itself and theelectric current path of the other writing line. In the following sixthto ninth embodiments, description will be given as to an example thatthe magnetization easy axis of the tunneling junction element isinclined substantially 30°-60° and arranged at the parallel wiringportion and the erroneous writing margin of the half-selected cell isthereby increased.

[0139] The essential feature will be first described before explainingthe sixth to ninth embodiments. The memory cell used in the magneticmemory device according to these embodiments has at least one tunnelingbarrier layer, a recording cell having a ferromagnetic tunnelingjunction having at least two ferromagnetic layers and at least oneantiferromagnetic layer, and two writing wirings arranged above andbelow the recording cell in parallel with each other, and the long axis(magnetization easy axis) direction of the recording cell has an angleof substantially 30°-60° with respect to the two writing wirings.Further, it is desirable that the two wiring wirings are surrounded by amagnetic shield material.

[0140] In these embodiment, as shown in FIG. 11, the upper and lowerwirings (the bit line 202 and the writing word line 203) of theferromagnetic tunneling junction (MTJ) cell 201 are arranged insubstantially parallel with each other at least at positions above andbelow the MTJ cell 201, and they are arranged in such a manner that themagnetization easy axis of the MTJ cell 201 is directed toward thedirection which is approximately 30°-60° relative to the wiringdirection. Furthermore, a shield material 204 is applied to the wiringsabove and below the MTJ cell of the wirings over the wiring length whichis 1.2-fold or above of the longitudinal direction of the MTJ cell. Itis to be noted that reference numeral 205 denotes a reading word lineorthogonal to the bit line 202, or a wiring connected to a conductioncontrol (switching) element such as a transistor or a diode, and 206designates an insulation layer which insulates the wiring 205 and thewriting word line. The MTJ element 201 is sandwiched and connectedbetween the bit line 202 and the wiring 205.

[0141] On the other hand, in the prior art magnetic memory element, asshown in FIG. 12, the bit line 302 and the writing word line 303 areorthogonal to each other, and the MTJ cell 301 is sandwiched andconnected between the bit line 302 and the wiring 305 in such a mannerthat the magnetization easy axis of the MTJ cell 301 is directed to thebit line direction. It is to be noted that reference numeral 305 denotesa reading word line, or a wiring connected to a conduction controlelement such as a transistor or a diode, and 306 designates aninsulation layer which insulates the wiring 305 and the writing wordline 303.

[0142] In case of using the above-described structure, when the pulsecurrents in opposite directions are caused to flow to the upper andlower parallel wirings, the switching magnetic field curve is deformedas indicated by A in FIG. 13, and writing can be carried out with asmaller magnetic field than that of the prior art asteroid curve B.

[0143] In detail, in the conventional cross point architecture such asshown in FIG. 12, the asteroid curve is as indicated by B in FIG. 13.When the magnetic field outside this curve is given, inversion of thespin occurs. As apparent from FIG. 13, when a synthetic magnetic fieldof the magnetic field generated by the upper wiring and the magneticfield generated by the lower wiring has a direction of 45°, inversion ofthe spin occurs with the smallest magnetic force. Therefore, when themagnetization easy axis of the MTJ element 201 is inclined bysubstantially 45° with the bit line 201 and the writing word line 203being parallel to each other, the switching magnetic field curve can beminimized as indicated by A in FIG. 13.

[0144] In case of such a structure, even if the wiring rule is reducedto 0.1 μm and a distance between adjacent cells is decreased, there isno problem of crosstalk since the shield material 204 is applied to thewirings 202 and 203 and the switching magnetic field curve has anadvantageous shape with respect to crosstalk.

[0145] In case of this structure, it is preferable that the length ofthe shield material 204 applied to the wirings 202 and 203 is at least1.2-fold or above of the length of the MTJ cell 201 in the longitudinaldirection. When the length of the shield material 204 is longer thanthis length, the advantage that the shield material 204 reinforces theelectric current magnetic field can be provided, and hence the switchingmagnetic field curve can be decreased in the direction along which theswitching magnetic field becomes smaller.

[0146] Concrete embodiments which realize the above structure will nowbe described as the sixth to ninth embodiments.

[0147] (Sixth Embodiment)

[0148]FIG. 14 is a typical connection diagram showing a structure of amemory cell array (magnetic memory device) according to the sixthembodiment, and the memory cell has an architecture of a simple matrixwhich does not include a switching element such as a diode or atransistor.

[0149] A plurality of bit lines BL (second writing lines) and aplurality of reading word lines WL substantially vertically cross eachother, and an MTJ cell 201 is connected between the bit line BL and thereading word line WL at each intersection. A writing word line WL′(first writing line) is provided in parallel with each bit line, and thewriting word line WL′ and the bit line BL cross each other with an angleof substantially 45 degrees relative to the direction of the easy axisof the MTJ cell. As shown in FIG. 11, a magnetic shield is applied tothese bit lines BL and the writing word lines WL′. There are provided acolumn decoder 211 which selects the reading word line WL and a rowdecoder 212 which selects the bit line BL and the writing word line WL′outside the memory cell array.

[0150] Incidentally, although a number of each of the bit lines BL, thereading word lines WL and the writing word lines WL′ is only three inFIG. 14, a desired number of such lines may be provided. This can besimilarly applied to the connection diagram in the later-describedembodiments.

[0151] Since writing is enabled with a smaller magnetic field than thatin the prior art when the above-described structure is adopted, powerconsumption during the writing operation is lowered, andelectromigration is also suppressed, thereby providing the memory andthe wiring structure having no crosstalk.

[0152] Meanwhile, when using this architecture, since the resistance ofthe MTJ cell must be larger than those of the bit line BL and thewriting word line WL′, it is preferable that a number of the MTJ cellsper block of the memory is not more than 10 Kbit, and more preferablynot more than 3 Kbit.

[0153] (Seventh Embodiment)

[0154]FIG. 15 is a typical connection diagram showing a structure of amemory cell array (magnetic memory device) according to the seventhembodiment. The memory cell array according to this embodiment has anarchitecture in which bit lines BL, reading word lines WL crossing thebit lines BL, and writing word lines WL′ parallel to the bit lines BLare arranged in the matrix of the memory cell comprised of MTJ cells 201and diodes 207 each of which is connected to this cell, as similar tothe sixth embodiment.

[0155] Furthermore, in the seventh embodiment, the magnetization easyaxis of the MTJ cell 201 forms an angle of substantially 30-60 degreesrelative to the bit line BL and the writing word line WL′, and amagnetic shield (not shown) is applied to the bit line BL and thewriting word line WL′.

[0156] As a result, the advantage similar to that of the sixthembodiment can be obtained, and addition of the diode 207 to the MTJelement 201 in series can realize the active matrix type memory cellarray.

[0157] (Eighth Embodiment)

[0158]FIG. 16 is a typical connection diagram showing a structure of amemory cell array (magnetic memory device) according to an eighthembodiment. The memory cell array according to this embodiment has anarchitecture in which bit lines BL, reading word lines WL crossing thebit lines BL, and writing word lines WL′ parallel to the bit lines BLare arranged in a matrix of the memory cell comprised of MTJ cells 201and MOSFETs 208, as similar to the sixth embodiment.

[0159] In this architecture, the magnetization easy axis of the MTJ cell1 likewise forms an angle of substantially 30-60 degrees relative to thebit line BL and the writing word line WL′, and a magnetic shield (notshown) is applied to the bit line BL and the writing word line WL′.

[0160] As a result, the advantage similar to that of the sixthembodiment can be obtained, and adding the MOSFET 208 to the MTJ element201 can realize the active matrix type memory cell array.

[0161] As a concrete example, description will now be given as to anexample in which a test element (TEG1) having the 3×3 cell matrix wasfabricated by using the memory cell according to this embodimentcomprised of the MOSFETs and the MTJ cells. For the purpose ofcomparison, a test element (TEG2) having the 3×3 cell matrix structurewas fabricated with the architecture of the regular MOSFETs and MTJcells shown in FTG. 12, and the switching magnetic field characteristicswere compared. In regard to wirings, there were used the Al—Cu wiring,the wiring rule of 0.175 μm, and an aspect ratio of the wiring crosssection being 1:2. The wiring whose cross section is longer in thevertical direction than the horizontal direction was used.

[0162] The both MTJ cells had an elliptical shape, and the magnetizationeasy axis of the MTJ cell was inclined approximately 45° relative to thewirings (the bit lines and the writing word lines) in the TEG1 using thestructure according to this embodiment (FIG. 11). A shield material wasfabricated by the plating method using Ni—Fe. Before film formation ofeach wiring, plating processing was carried out, and a distance betweenthe MTJ cell and the bit line BL or the writing word line WL′ wasdesigned to be nearly same in the both test elements.

[0163] In the both test elements, the ferromagnetic double tunnelingjunction (Ta/IrMn/(CoFe/Ru/CoFe)/AlO_(x)/Ni—Fe/AlO_(x)/(CoFe/Ru/CoFe)/IrMn/Ta) was used for the MTJ cell.

[0164] For the MTJ cell, film formation was carried out by using anultra-high vacuum sputtering device, and AlO_(x) was fabricated by themethod which performs plasma oxidation after film formation of Al. FIG.17 shows a switching magnetic field curve C when using the architectureof this embodiment, and a switching magnetic field curve D when using aregular architecture illustrated in FIG. 12. As shown in FIG. 17, it wasconfirmed that the switching magnetic field curve according to thisembodiment was considerably minimized and it is possible to provide thememory structure which can reduce power consumption during the writingoperation and does not cause a problem of crosstalk andelectromigration.

[0165] (Ninth Embodiment)

[0166]FIG. 18 is a typical connection diagram showing a structure of amemory cell array (magnetic memory device) according to the ninthembodiment. Although the memory cell array according to this embodimenthas an architecture in which bit lines BL and reading word lines WLsubstantially orthogonal to each other are arranged in a matrix of thememory cell comprised of MTJ cells 201 and MOSFETs 208, writing wordlines WL′ are arranged in parallel to the reading word lines WL, and thebit lines BL and the writing word lines WL′ are parallel to each otheronly at positions where they run above or below the MTJ cells 201.

[0167]FIG. 19 is a typical plan view showing the wiring state of a part19 in FIG. 18. In this case, the word line WL′ is an underpart wiring,and the bit line BL is an upper wiring. Also, the MTJ element 201 isconnected to the lower plane of the bit line BL, and the magnetizationeasy axis of the MTJ element 201 is arranged so as to be inclinedapproximately 45° relative to the bit line BL and the part of the wordline WL′ arranged under the bit line BL in the insulating manner.

[0168]FIG. 20 is a typical cross-sectional view of the memory cellportion in FIG. 18, and the upper half part of this drawing shows thepositional relationship of the upper wiring (BL) and the underpartwiring (WL′) illustrated in FIG. 19 in the cross-sectional manner. Thatis, although the underpart wiring (WL′) is arranged vertically to theupper wiring (BL) in the right part in FIG. 20, it is parallel to theupper wiring (BL) in the central part in FIG. 20, and the MTJ cell 201and the diode 209 are sandwiched between the underpart wiring and theupper wiring.

[0169] However, the diode 209 is not necessary when the resistance ofthe MTJ cell 201 is approximately five times larger than the Onresistance of the MOSFET 208. Although not apparent in thecross-sectional view, the MTJ cell 201 is arranged in such a manner thatits magnetization easy axis is inclined approximately 45° relative tothe upper wiring and the underpart wiring.

[0170] If the above-described structure is adopted, the advantagesimilar to that in the eighth embodiment can be obtained. Also, sincewiring the reading word line WL and the writing word line WL′ in thesame direction can suffice, arrangement of the word line drive circuit(decoder) can be simplified.

[0171] In the sixth to ninth embodiments, a column decoder 211 and a rowdecoder 212 used for selecting the bit line BL, the reading word line WLand the writing word line WL′ are arranged around the memory cell array,and “1” or “0” is judged based on whether a signal voltage from the MTJcell is larger or smaller than that from a reference cell (not shown)arranged for each memory block.

[0172] As to a voltage value of the reference cell, it is preferable touse the reference cell having a voltage value which is between a voltagevalue in the state that arrangement of adjacent spins having a highsignal voltage of the MTJ cell is anti-parallel and a voltage value inthe state that arrangement of adjacent spins having a small signalvoltage is parallel.

[0173] As described above, the first to fifth embodiment have disclosedthe technique for inclining the synthetic magnetic field obtained fromthe upper writing line and the lower writing line with respect to themagnetization easy axis and facilitating inversion of magnetization, andthe sixth to ninth embodiment have disclosed the technique for arrangingthe MTJ cell, whose magnetization easy axis is inclined approximately30-60 degrees, at a parallel portion of the upper writing line and thelower writing line and facilitating inversion of magnetization. In orderto further facilitate magnetization inversion, utilization of a yoke ora magnetic bias film can be considered. As the extension of the first tofifth embodiments, embodiments having a yoke or a magnetic bias filmadded thereto will now be described hereinafter as tenth to 12thembodiments.

[0174] (Tenth Embodiment)

[0175]FIG. 21 is a plan view typically showing from a substrate surfaceside a cell layout according to the tenth embodiment. FIG. 22A is across-sectional view of a memory cell taken along the line 22A-22A inFIG. 21, and FIG. 22B is a cross-sectional view of the memory cell takenalong the line 22B-22B in FIG. 21. It is to be noted that like referencenumerals denote parts equal to those in the first embodiment.

[0176] In FIG. 21, reference numerals 11 and 12 denote first writinglines; 21 and 22, second writing lines; 101 and 102, MTJ cells; and 31and 32, contact holes. Further, in FIGS. 11A and 11B, reference numeral41 designates a lower electrode; 501 and 502, diffusion areas ofselected transistors; and 51, a word line of a selected transistor. Thefirst writing line and the second writing line are electricallyinsulated. Furthermore, the second writing line is electricallyconnected to the MTJ element and also serves as a data line.

[0177] In FIGS. 21, 22A and 22B, reference numeral 601 denotes a lowermagnetic circuit; 602, a magnetic flux guide (yoke); and 603, an uppermagnetic circuit. They form magnetic shields 61 and 62.

[0178] The basic cell arrangement in the tenth embodiment is the same asthat of the third embodiment. In this embodiment, the magnetic shield isapplied to the first writing wiring and the second writing wiring in thevicinity of the MTJ cell. The magnetic shield according to thisembodiment is configured to converge the magnetic fields obtained fromthe two wirings to the vicinity of the MTJ element by using the lowermagnetic circuit and the upper magnetic circuit respectively and applythe converged magnetic field to this element by using the magnetic fluxguide.

[0179] The magnetic shield is formed in parallel with the first andsecond writing lines. The direction of the magnetic field generated fromthe second writing line is parallel to the magnetization easy axis ofthe magnetic shield. It is preferable that the length of the magneticshield is at least 1.5-fold or above of the length of the element in thewriting line direction.

[0180] As a material used for the magnetic shield, it is possible to usepermalloy which is a high-permeability magnetic material, Ni group alloysuch as permalloy having Mo added thereto, and Fe group alloy such asSendust. Also, an oxide ferromagnetic material such as ferrite can beused.

[0181] The pulse width of the writing electric current is usually notmore than 100 ns during the MRAM writing operation. Therefore, themagnetic shield material must have the characteristic that themagnetization response can follow the writing current pulse. For thispurpose, it is desirable to satisfy conditions (1) that the permeabilityis at least not less than 100 when the magnetic field is just over zero,(2) that saturation magnetization is small and (3) that the specificresistance of the material is high. In order to satisfy theseconditions, adding an additive to the alloy, or adding metalloid such asSi or B or an additive from which a grain boundary precipitation such asCu, Cr or V can be easily produced and forming a microcrystal aggregateor amorphous is a preferable conformation.

[0182] Moreover, optimizing the shape is more preferable for the purposeof controlling the magnetic domain in the magnetic shield.

[0183] The magnetic shield has advantages of (1) that it can effectivelyapply the magnetic field generated from the wiring to the MTJ cell inorder to converge the magnetic flux generated around the wiring into themagnetic circuit, (2) that the magnetic field of the layer can bereinforced by optimizing the structure in such a manner that the passingmagnetic flux of the magnetic circuit can be effectively applied to thevicinity of the element, and (3) that the erroneous writing marginrelative to the half-selected cell can be increased since the leakageflux from the wiring can be intercepted by the magnetic circuit. Inparticular, as with this embodiment, when the MTJ cell is configured tobe completely covered with the upper magnetic circuit and the lowermagnetic circuit, not only the advantage of (3) can be improved, butalso a new advantage that the effect of the magnetic shield can beprovided to the external magnetic field. In this case, the externalmagnetic filed includes the magnetic field from the neighboring wiring.

[0184] In the cell structure according to this embodiment shown in FIG.23, of the magnetic field Hx generated at the bent portion of the firstwriting line, a component parallel to the direction of the magneticfield Hy generated by the second writing line is reinforced by themagnetic shield, but a component vertical to Hy is not reinforced by themagnetic shield. That is, the magnetic shield of this embodiment has afunction of selecting only a unidirectional component in the magneticfield in an arbitrary direction from the wiring and reinforcing it.

[0185] (11th Embodiment)

[0186] In the tenth embodiment, since a component in Hx which isparallel to the direction of the magnetic field Hy generated by thesecond writing line is reinforced, the magnetic field component in thedirection of the magnetization hard axis effectively becomes very small.Similarly, when the magnetic field component from the wiring in thedirection of the magnetization hard axis is very small, or when themagnetic field component in the direction of the magnetization hard axisdoes not exist, the operation point setting such as described in thefirst embodiment is difficult if used as it is.

[0187] In order to improve this problem, as typically shown in FIGS. 24Aand 24B, it is effective to arrange bias films 701 and 702 in thevicinity of the MTJ cell 101 and apply the bias magnetic field in thedirection of the element hard axis. It is good enough to set themagnetization direction of the bias films 701 and 702 to the directionof the magnetic field which should be applied to the MTJ cell. Forexample, in order to apply the magnetic field along the hard axis of theMTJ cell, setting the magnetization direction of the bias film so as tobe parallel to the magnetization hard axis can suffice.

[0188] As to arrangement of the bias films 701 and 702, there are amethod to arrange the bias films adjacent to the MTJ cell 101 as shownin FIG. 24A and a method to arrange them so as to overlap the MTJ cellas shown in FIG. 24B.

[0189] As to the former method, control is easy since the intensity ofthe bias magnetic field varies depending on a distance between the MTJcell 101 and the bias film, but it is hard to increase the intensity ofthe bias magnetic field.

[0190] In regard to the latter method, there can be considered the threecases, i.e., when the MTJ cell 101 is directly connected to the biasfilms 701 and 702 in the switched manner, when interlayer couplingthrough a non-magnetic film and an insulation film is provided, and whenmagnetic coupling is hardly provided. When there is any magneticcoupling between the MTJ cell 101 and the bias films 701 and 702, theintensity of the bias magnetic field can be sufficiently increased,which is advantageous. Further, magnetic domain control caused at an endof the MTJ cell 101 can be effectively carried out.

[0191] As the bias film, it is possible to use (1) a high-coercivitymagnetic film having higher coercivity than that of the MTJ cell 101 and(2) a soft magnetic film having lower coercivity than that of the MTJcell 101.

[0192] In case of (1), the bias film can be arranged inside the magneticflux guide 602 forming the magnetic shield 61. In such a case, intensityof the anisotropic magnetic field of the bias film must be sufficientlyhigher than that of the magnetic field generated in the magnetic fluxguide 602.

[0193] As such a bias film, for example, it is possible to use hardmagnetic alloy such as CoPt alloy or a Co/Pt multi-layer film, amulti-layer film, a multilayer film having the strong interlayercoupling such as a Co/Cu multi-layer film, a laminated film of anantiferromagnetic material such as PtMn and the hard magnetic alloy, andothers. In this case, besides having the large anisotropic magneticfield, sufficiently high saturation magnetization of the film isnecessary.

[0194] In case of (2), it is difficult to arrange the bias film insidethe magnetic flux guide 602 forming the magnetic shield 61, and it mustbe arranged outside the magnetic flux guide 602. Outside the magneticflux guide 602, the direction of a line of magnetic force has acomponent in the direction of the magnetization hard axis because of theinfluence of the magnetic pole at the end of the magnetic flux guide602. When such a soft magnetic film as that magnetization inversion iscaused to the magnetization hard axis of the MTJ cell due to thecomponent in the magnetization hard axis is used for the bias film, itis possible to provide the effective bias magnetic field in thedirection of the hard axis.

[0195] As such a bias film, for example, it is possible to use softmagnetic alloy such as NiFe alloy and amorphous alloy. In this case, notonly the magnetic field must have the high permeability in the vicinityof zero, but also saturation magnetization of the film must besufficiently large.

[0196] Description will be given as to the sell selection operation whensuch a bias magnetic field is applied with reference to FIG. 25. Here,it is assumed that the generated magnetic fields together with the firstand second writing lines are parallel to the magnetization easy axis ofthe tunneling junction element. As shown in the drawing, in the selectedcell, since the magnetic field along the hard axis Hb exists in additionto the magnetic fields Hx+Hy in the direction of the easy axis, thesynthetic magnetic field exceeds the switching threshold value. On theother hand, in the half-selected cell, the magnetic field along the easyaxis is either Hx or Hy. Also, even if the magnetic field along the hardaxis Hb is synthesized, it does not exceed the switching thresholdvalue.

[0197] As in this embodiment, when the bias magnetic field is applied bythe bias film, the current value required for the writing operation canbe reduced. When the current value is reduced, not only powerconsumption is reduced, but also improvement in the erroneous writingmargin of the half-selected cell and improvement in duration of life ofthe wirings can be expected, thereby increasing the advantage.

[0198] (12th Embodiment)

[0199]FIG. 26 is a plan view typically showing from the substrate side acell layout according to the 12th embodiment of the present invention.FIG. 27A is a cross-sectional view of a memory cell taken along the line27A-27A in FIG. 26, and FIG. 27B is a cross-sectional view of the memorycell taken along the line 7B-7B in FIG. 26.

[0200] In FIG. 26, reference numerals 11 and 12 denote first writinglines; 21 and 22, second writing lines; and 101 and 102, MTJ elements.Further, in FIGS. 27A and 27B, reference numeral 41 designates a lowerelectrode; 601, a magnetic circuit; 602, a magnetic flux guide; and 61and 62, magnetic shields. The first writing line and the second writingline are electrically connected through to the lower electrode and theMTJ cell, and also serve as sense current circuits with respect to theMTJ cell.

[0201] Although the structure of this embodiment is equal to that of thetenth embodiment, it is characterized in that the first writing line andthe second writing line are positioned on the same plane in the vicinityof the MTJ cell. This structure is suitable for application to agranular tunneling junction element such that a tunneling current flowssubstantially in the film plane, or a planar tunneling junction elementof, e.g., a lamp edge type.

[0202] During the writing operation, although a potential differenceoccurs between the first and second writing lines, a preferableconformation is that the lower electrode 41 is configured by an elementhaving rectification for the purpose of reducing the influence of aleakage current, destruction of the element or the like.

[0203] Description will now be given as to an embodiment of the magneticmemory device in which a soft magnetic bias layer is given to the memorycell having the ferromagnetic tunneling junction including at least onetunneling barrier layer, at least two ferromagnetic layers and at leastone antiferromagnetic layer in the direction of the magnetization easyaxis of the memory cell.

[0204]FIG. 28 is a view showing the MTJ cell from above. In thisembodiment, a soft magnetic bias layer 210 is given adjacent to a memorylayer of the MTJ cell 201. In the bias layer 210, when the magneticfield does not exist (H=0), an edge domain is generated at the end.However, when the bias magnetic field is given, the spin inverts. Inthis manner, since the soft bias layer first inverts in accordance withthe electric current magnetic field, the switching magnetic field of theMTJ cell 201 becomes small due to the bias magnetic field from the softmagnetic layer.

[0205]FIG. 21 shows the rectangular MTJ cell shape, and FIG. 11 showsthe elliptical MTJ cell shape. However, the cell shape does not have tobe rectangular or elliptical. For example, it is possible to employvarious cell shapes such as shown in FIGS. 29A to 29D. FIGS. 29A and 29Bshow examples of the above-described elliptical and circular MTJ cellshapes, and FIGS. 29C and 29D show examples of rhomboidal andparallelogram MTJ cell shapes. Any shape can be used for the soft biaslayer. When elliptical, circular, parallelogram and rhomboidal shapesare used, however, the bias magnetic field is effectively applied sincethe structure is similar to a single magnetic domain structure, and theerroneous operation is reduced. Furthermore, in case of the circularshape, the cell structure becomes minimum, which is preferable.

[0206] Moreover, by controlling the soft magnetic layer and the MTJ cellto sub-micron or a smaller unit, the electrostatic magnetic coupling isgenerated between the MTJ cell and the soft magnetic layer. Therefore,as shown in FIG. 29B, the magnetization easy axis can be defined in thedirection of the soft magnetization layer without employing theelongated shape of the MTJ cell 201 as shown in FIG. 29B. Also, since anarea of the cell can be reduced, the magnetic memory device with thehigher capacity (MRAM) can be manufactured. In such structures, thecircular structure shown in FIG. 29B demonstrates the minimum switchingmagnetic field.

[0207] In addition, when the sixth to ninth embodiments are combined andused, the switching magnetic field becomes minimum. In such a case, itis preferable to incline the axial direction connecting the soft biaslayers to the direction of approximately 45° relative to the wiringdirection. A 13th embodiment is such an example.

[0208] (13th Embodiment)

[0209] In the 13th embodiment, a test element (TEG3) of the 3×3 cellmatrix having the eighth element (FIG. 16) structure including the MTJcell 1 and the MOSFET having the FIG. 29B structure and a test element(TEG4) of the 3×3 cell matrix structure according to the eighthembodiment (FIG. 16) having the simple elliptical MTJ cell weremanufactured, and their switching magnetic field characteristics werecompared.

[0210] In regard to a wiring, an Al—Cu wiring was used, and it wasdetermined the wiring rule is 0.25 μm and the cross-sectional aspectratio of the wiring is 1:2. In addition, the wiring whose cross sectionis longer in the vertical direction than the horizontal direction wasused. In the both test elements, the magnetization easy axis of the MTJcell is inclined to the direction of 45° with respect to the wirings(the bit line BL and the writing word line WL′). Ni—Fe was used as ashield material, and the CVD method was employed for manufacturing.Before film formation of each wiring, CMP processing was carried out,and a distance between the MTJ cell and the bit line BL or the writingword line WL′ was designed to be equal in the both test elements. As theMTJ cell, the ferromagnetic double tunneling junction(Ta/Ni—Fe/Pt—Mn/(CoFe/Ru/CoFe)/AlOx/(Co—Fe—Ni/Cu/Co—Fe—Ni)/AlOx/(CoFe/Ru/CoFe)/Pt—Mn/Ta)was used in the both test elements.

[0211] Film formation of the MTJ cell 201 was performed by using anultra-high vacuum sputtering device, and AlO_(x) was manufactured by themethod which effects plasma oxidation after forming a film of Al. FIG.30 shows the switching magnetic field curves when using the architecture(TEG3) according to the 13th embodiment (E) and when using the structure(TEG4) according to the eighth embodiment (F). As illustrated in FIG.30, the switching magnetic field curve according to the eighthembodiment is considerably reduced as compared with the eighthembodiment. As a result, power consumption during the writing operationis decreased, and it was confirmed that a memory structure which doesnot generate problems of crosstalk and EM can be provided.

[0212] Incidentally, although description has been given as to theexample of the combination of the eighth embodiment and the softmagnetic bias layer in the 13th embodiment, the combination is notrestricted to the eighth embodiment, and the soft magnetic bias layercan be combined with the first to seventh and ninth embodiments.

[0213] The magnetic memory device described in connection with the firstto 13th embodiments is preferable to be mounted in a memory portion of,e.g., a mobile phone.

[0214] Incidentally, in the first to 13th embodiments, as the MTJelement (cell) structure, it is preferable to adopt a so-called spinvalve type which provides the antiferromagnetic layers 221 and 231 asshown in FIGS. 31 and 32. Incidentally, in FIG. 31, reference numerals222 and 224 denote ferromagnetic layers and 223 designates a tunnelingbarrier layer, and this drawing shows the tunneling junction structurehaving at least one tunneling barrier layer, at least two ferromagneticlayers and at least one antiferromagnetic layer. Additionally, in FIG.32, reference numerals 232, 234 and 236 denote ferromagnetic layers; 233and 235, tunneling barrier layers; and 231 and 237, antiferromagneticlayers.

[0215] Further, the ferromagnetic layer (magnetically pinned layer) 232can be, as shown in FIG. 33, substituted by a so-calledantiferromagnetic coupling layer in which the three-layer structure of(the ferromagnetic layer 232-1/the nonmagnetic layer 238/theferromagnetic layer 232-2) realizes the antiferromagnetic couplingthrough the nonmagnetic layer.

[0216] Since the spin of the pinned layer can be further strongly fixedby using this three-layer structure as the pinned layer, there can beobtained merits that some magnetic moments of the pinned layer arecaused to rotate due to writing for several times and the output isgradually lowered and that a film thickness of the antiferromagneticfilm can be reduced and the forming accuracy can be increased, therebyreducing irregularities in the switching magnetic field.

[0217] Furthermore, it is preferable to use the three-layer structure of(the ferromagnetic layer/the nonmagnetic layer/the ferromagnetic layer)for the magnetic recording layer. In this case, it is preferable toprovide the ferromagnetic layer coupling between the ferromagneticlayers. When this structure is used for the magnetic recording layer,the dependency of the switching magnetic field on the cell width issmall, and increase in the switching magnetic field is small even if thecell width is reduced, which increases the capacity of the MRAM. Also,even if the cell width of the MTJ element is reduced, there is noproblem of increase in power consumption or electromigration of thewirings during the writing operation, thus manufacturing the MRAM withthe higher capacity. The smaller intensity of the ferromagnetic couplingis preferable, and the switching magnetic field becomes smaller as theintensity is lowered.

[0218] In this embodiment, elements and types of the ferromagnetic layerare not restricted in particular, and it is possible to use Fe, Co, Ni,or alloy of such materials, magnetite having the high spinpolarizability, oxides such as CrO₂, RXM_(n)O_(3-y) (R: rear earth, X:Ca, Ba, Sr), Heusler alloy such as NiMnSb, PtMnSb, or a magneticsemiconductor such as Zn—Mn—O, Ti—Mn—O, CdMnP₂, AnMnP₂.

[0219] The ferromagnetic layer used in the embodiments according to thepresent invention must have a film thickness such that thesuperparamagnetism is not provided, and it is preferable that the filmthickness is not less than 0.4 nm. Further, if the film thickness isvery large, the switching magnetic field and the magnetostatic leakagefield become large. Therefore, the film thickness should be preferablynot more than 3.0 nm. Furthermore, even if a nonmagnetic element such asAg, Cu, Au, Al, Mg, Si, Bi, Ta, B, C, O, N, Pd, Pt, Zr, Ir, W, Mo or Nbis included in these magnetic materials to a certain degree, this can beallowed as long as the ferromagnetism is not lost.

[0220] As the antiferromagnetic film, it is possible to use Fe—Mn,Pt—Mn, Pt—Cr—Mn, Ni—Mn, Ir—Mn, Ru—Mn and others. In case of using thethree-layer film of the ferromagnetic layer/the nonmagnetic layer/theferromagnetic layer for a free (recording) layer, Cu, Au, Ru, Ir, Rh, Agand others can be used for the nonmagnetic layer.

[0221] As the dielectric material or the insulating layer, it ispossible to use various dielectric materials such as Al₂O₃, SiO₂, MgO,AlN, AlON, GaO, Bi₂O₃, SrTiO₂, AlLaO₃ and others. Oxygen or nitrogen maybe lost to a certain degree in these materials.

[0222] It is preferable that a thickness of the dielectric layer dependson a junction area of the MTJ element and is not more than 3 nm. Asubstrate material is not restricted to a specific type in particular,and Si, SiO₂, Al₂O₃, AlN or the like can be manufactured on thesubstrate. It is preferable to use as an underlying layer and aprotection layer, Ta, Ti, Pt, Au, Ti/Pt, Ta/Pt, Ti/Pd, Ta/Pd or the likeon the substrate.

[0223] Such a magnetoresistive element (MTJ element) can be manufacturedby using a regular thin film forming device which adopts various kindsof sputtering methods, evaporation methods, molecular beam epitaxymethods or the like.

[0224] As described above, according to the present invention, it ispossible to provide the high-density magnetic memory device which cangreatly reduce power consumption during the writing operation andeliminate problems of the conventional magnetic memory device (MRAM),that is, large power consumption, crosstalk, electromigration (EM) andothers.

[0225] Additional advantages and modifications will readily occur tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to the specific details and representativeembodiments shown and described herein. Accordingly, variousmodifications may be made without departing from the spirit or scope ofthe general inventive concept as defined by the appended claims andtheir equivalents.

What is claimed is:
 1. A magnetic memory device comprising: a pluralityof magnetoresistive elements arranged on a first plane in rows andcolumns; a plurality of first writing lines arranged adjacent to saidmagnetoresistive elements on a second plane different from said firstplane; a first address decoder which selects a desired one from saidplurality of first writing lines; a plurality of second writing linescrossing said plurality of first writing lines on a third planedifferent from said second plane, and having parts adjacent to saidplurality of magnetoresistive elements and parallel to said plurality offirst writing lines; and a second address decoder which selects adesired one from said plurality of second writing lines.
 2. The magneticmemory device according to claim 1, wherein said plurality ofmagnetoresistive elements are respectively provided directly above saidplurality of first writing lines, each of said magnetoresistive elementshas at least two ferromagnetic layers and at least one tunneling barrierlayer therebetween, and a magnetization easy axis thereof has an angleof substantially 30°-60° relative to said plurality of first writinglines; and at least one of said plurality of first and second writinglines are connected to said plurality of magnetoresistive elements. 3.The magnetic memory device according to claim 2, wherein said pluralityof first writing lines and said plurality of second writing lines have aplurality of magnetic shields which intercept influence of an externalmagnetic field at least in the vicinity of said plurality ofmagnetoresistive elements.
 4. The magnetic memory device according toclaim 1, further comprising a plurality of high-coercivity magneticfilms configured to apply a bias magnetic field to said plurality ofmagnetoresistive elements.
 5. The magnetic memory device according toclaim 1, further comprising: a plurality of magnetic circuits which holdmagnetic fields generated from said plurality of first writing lines andsaid plurality of second writing lines; and a plurality of magnetic fluxguides which concentrate magnetic fluxes passing through said pluralityof magnetic circuits on said plurality of magnetoresistive elements. 6.The magnetic memory device according to claim 1, wherein said pluralityof first writing lines and said plurality of second writing lines arearranged on planes different from a plane where said plurality ofmagnetoresistive elements are arranged to sandwich said plurality ofmagnetoresistive elements therebetween in a direction vertical to saidfirst plane.
 7. The magnetic memory device according to claim 1, whereinin said parts said plurality of second writing lines are arranged on thesame plane as said plurality of first writing lines.
 8. The magneticmemory device according to claim 1, wherein selection is carried out bygiving column and row addresses of a selected element to said firstaddress decoder and said second address decoder, respectively, and datais selectively written into said plurality of magnetoresistive elements.9. The magnetic memory device according to claim 1, wherein each of saidplurality of magnetoresistive elements has at least two ferromagneticlayers and at least one tunneling barrier layer therebetween, and saidat least one layer of ferromagnetic layers comprises a laminated layerincluding a three-layer structure of a ferromagnetic layer/a nonmagneticmetal layer/a ferromagnetic layer.
 10. The magnetic memory deviceaccording to claim 1, further comprising: a plurality of word lines forreading which cross a plurality of bit lines, said bit lines comprisingsaid plurality of either first or second writing lines; and switchingelements which are provided at respective intersection regions of saidplurality of bit lines and said plurality of word lines and connected tosaid magnetoresistive elements in series.
 11. A magnetic memory devicecomprising: a first writing line arranged on a first plane; a secondwriting line arranged on a second plane different from said first planeand has a first part extended from one direction vertical to said firstwriting line, a second part connected to said first part at one endportion thereof and overlaps said first writing line, and a third partconnected to said second part at the other end portion thereof, andextended vertically to said first writing line on an opposite side ofsaid first part, the relationship of 2a>b>0 being provided wherein a isa line width of said first and said second writing line and b is ashortest distance between a central line of said first part and acentral line of said third part of said second writing line; and amagnetoresistive element sandwiched between said first writing line andsaid second part of said second writing line and connected to eithersaid first writing line or said second writing line.
 12. The magneticmemory device according to claim 11, further comprising ahigh-coercivity magnetic film configured to apply a bias magnetic fieldto said magnetoresistive element.
 13. The magnetic memory deviceaccording to claim 11, further comprising: a magnetic circuit whichholds magnetic field generated from said first writing line and saidsecond writing line; and a magnetic flux guide which concentratesmagnetic fluxes passing through said magnetic circuit on saidmagnetoresistive element.
 14. The magnetic memory device according toclaim 11, wherein said first writing line and said second writing lineare arranged on planes different from a plane where saidmagnetoresistive element is arranged to sandwich said magnetoresistiveelement therebetween in a direction vertical to said first plane. 15.The magnetic memory device according to claim 11, further comprising: aplurality of first writing lines in units of said first writing line; aplurality of second writing lines in units of said second writing line;a plurality of magnetoresistive elements in units of saidmagnetoresistive element; a first address decoder which selects adesired one from said plurality of first writing lines; and a secondaddress decoder which selects a desired one from said plurality ofsecond writing lines, wherein selection is carried out by giving columnand row addresses of a selected element to said first address decoderand said second address decoder, and data is selectively written intosaid plurality of magnetoresistive elements.
 16. The magnetic memorydevice according to claim 11, wherein each of said magnetoresistiveelements has at least two ferromagnetic layers and at least onetunneling barrier layer therebetween, and at least one layer of saidferromagnetic layers comprises a laminated layer including a three-layerstructure of a ferromagnetic layer/a nonmagnetic metal layer/aferromagnetic layer.
 17. A magnetic memory device comprising: aplurality of ferromagnetic tunneling junction elements arranged in amatrix form on a first plane and each of which has at least twoferromagnetic layers including a magnetic recording layer and at leastone tunneling barrier layer therebetween; and a plurality of softmagnetic bias layers provided at both ends of said plurality offerromagnetic tunneling junction elements in a direction of amagnetization easy axis and having magnetism softer than said magneticrecording layer.
 18. The magnetic memory device according to claim 17,wherein at least one layer of said ferromagnetic layers comprises alaminated layer including a three-layer structure of a ferromagneticlayer/a nonmagnetic metal layer/a ferromagnetic layer.
 19. The magneticmemory device according to claim 17, further comprising: a plurality offirst writing lines arranged on a second plane different from a firstplane, on which said plurality of ferromagnetic tunneling junctionelements are formed, adjacent to said ferromagnetic tunneling junctionelements; and a plurality of second writing lines crossing said firstwriting lines on a third plane different from said second plane andhaving parts adjacent to said plurality of ferromagnetic tunnelingjunction elements and parallel to said plurality of first writing lines.20. The magnetic memory device according to claim 17, furthercomprising: a plurality of word lines for reading which cross aplurality of bit lines, said bit lines comprising said plurality ofeither first or second writing lines; and switching elements provided atrespective intersection regions of said plurality of bit lines and saidplurality of word lines and connected to said ferromagnetic tunnelingjunction elements in series.